Catheters may be used for many medical procedures, including inserting a guide wire, delivering a stent and delivering and inflating a balloon. Catheterization procedures are commonly performed for diagnosis and treatment of diseases of the heart and vascular systems. The catheterization procedure is generally initiated by inserting a guide wire into a blood vessel in the patient's body. The guide wire is then guided to the desired location, most commonly in one of the heart vessels or elsewhere in the vascular system. At this point, the catheter is slid over the guide wire into the blood vessel and/or heart. Once the catheter is in the desired position, the guide wire can then be removed leaving the catheter in location. Alternatively, in some procedures, the catheter is inserted without using a guide wire. The catheter may be used to pass ancillary devices into the body such as an angioplasty balloon, or to perform other diagnostic or therapeutic procedures.
For manual insertion of a catheter, the physician applies torque and axial push force on the proximal end of a guide wire to effect tip direction and axial advancement at the distal end. Robotic catheter system have been developed that may be used to aid a physician in performing a catheterization procedure such as a percutaneous coronary intervention (PCI). The physician uses a robotic catheter system to precisely steer a coronary guide wire and balloon/stent device in order to, for example, widen an obstructed artery. The physician relies on position feedback signals provided by both the robotic catheter system and a fluoroscopic imaging system in order to complete the procedure Robotic catheter systems, however, do not provide the force feedback the physician experiences when manually performing PCI. In order to provide force sensing capabilities, an appropriately selected load cell or rotary torque sensor could be used; however, these are costly devices which can drastically increase the required work space volume to perform the PCI procedure.
It would be desirable to provide a system and method for controlling a motor used to drive portions of the catheter system including sensing torque using the motor. In various embodiments, either a brushless DC (BLDC) motor or a stepper motor may be used to determine the load torque being exerted on the motor. Presenting the real time force and torque required to drive a coronary device in the patient may enhance the performance of the robotic catheter system.